H2S Monitoring and Emission Control at the Cerro Prieto Geothermal Field, Mexico

Abstract

Results of an ambient air monitoring program performed in the Cerro Prieto Geothermal Field (CPGF) are described in this article. According to this study, conducted since 1997 by Comision Federal de Electricidad (CFE), the main government owned Utility in Mexico; it has monitored ambient air concentrations of hydrogen sulfide (H2S) in the geothermal field as well as in the neighbor villages around the CPGF.
Environmental regulations have been reinforced in many countries for air quality emissions. In this particular case, since Cerro Prieto is located within the 60 mile border zone between United State and Mexico, special attention it is taken to all the atmospheric emissions associated with the operation of this geothermal facility.
In despite of there being no International standards for H2S, in countries like the USA there is a local regulation in the State of California for a maximum level of H2S gas in ambient air at 42 g/m3 (30 ppb) per hour average. Many other countries have a "short-term" (usually 30 minutes) standard, which range from 6 to 210 ppb (WHO, 1980). In Mexico there are no environmental H2S criteria, but labor standard sets a maximum of 10 ppm per hour over an eight hours journey.
A complete H2S analysis in conjunction with regular climate measurements is performed. Graphical results shown that the CPGF always comply Mexican's labor regulation and most of the time, an international standard criterion in the Mexicali Valley.